Evaporative fuel which has occurred in a fuel tank presents a cause of air pollution. Thus, a vehicle with an engine is generally loaded with an evaporative fuel treatment apparatus for suppressing the discharge (dissipation) of evaporative fuel into the air. The evaporative fuel treatment apparatus, for example, has the fuel tank and an intake system of the engine connected together by a purge pipe line equipped with a canister. This apparatus allows evaporative fuel, which has occurred within the fuel tank, to be once adsorbed to activated carbon within the canister, and also introduces the fuel, which has been adsorbed to the activated carbon, into the intake system of the engine in response to the manifold vacuum pressure of the engine to burn it together with fresh air.
In recent years, vehicles equipped with an engine and a driving motor, such as plug-in hybrid electric vehicles (PHEV) and hybrid electric vehicles (HEV), have come into practical use. In such a vehicle equipped with a driving motor, a period during which the engine is stopping, namely, a period during which fuel cannot be introduced from the canister into the intake system of the engine, may last for a relatively long time. Thus, a so-called sealed type evaporative fuel treatment apparatus has been developed which provides a sealing valve between the fuel tank and the canister, and which brings the sealing valve to a closed state while the engine is stopping (see, for example, Patent Document 1).
In the evaporative fuel treatment apparatus, when the fuel tank is sealed with the sealing valve, fuel within the fuel tank may evaporate due causes, such as a rise in ambient temperature, and the internal pressure of the fuel tank may be raised. If the interior of the fuel tank is in a high pressure state and the sealing valve is damaged, there is a possibility that the fuel leaks out in a large amount. From the viewpoint of preventing fuel leakage in a collision of the automobile, moreover, it is necessary to prevent damage to the sealing valve more reliably.